1. Field of the Invention
The present invention relates to a novel method for smoothing a layer comprising magnetic particles in a binder carried on the surface of a suitable carrier such as a web of film or paper.
2. The Prior Art
Magnetic tape has been available for many years wherein a layer containing magnetic particles in a binder of a malleable polymeric resin is carried by a web of paper or film. Also it is well known to apply narrow stripes of similar magnetic compositions along the edges of motion picture film to provide the sound track. For improved frequency response and the greatest fidelty in recording and playing back sound it is desirable that the surface of the magnetic layer be extremely smooth and that the product be uniform in thickness, so as to assure the least gap between head and effective surface and to permit foundation of a tight uniform roll. Long recording head life also requires great smoothness.
In the past, efforts have been made to secure these desirable conditions by passing a magnetic tape or a striped film between metal polishing rollers after the coating step. While good results have been secured in this way, there are certain disadvantages to such a technique. For example, dirt frequently collects on the polishing rollers and causes polishing defects. Furthermore, such rollers are extremely expensive to manufacture and maintain because of the perfect cylindricity and the perfect surface polishing that are necessary. Morever, it is in some instances advantageous to heat the polishing rollers if the desired results are to be obtained.